How to write reply to it department calling of information u/s 133(6) of income tax act, 1961

My client was a retired pensioner and he had been filing his income tax returns for the last 8 years. But he fails to file IT return for the AY 2013-14, because he was hospitalized at that time of filing the returns. While computing his tax liability it is found that some tax liability also (below 10,000/-) Now he got a letter from from IT department calling of information u/s 133(6) of Income Tax Act, 1961. It is because of the deposit he made with some co-operative banks. Now they seek information about last 5 years IT returns statement along with computations. How to write a reply to IT department? Since it is the IT for AY 2013-14, I think 2 options. Pay the Tax for 2013-14 and admit that IT returns were not filed. Just admit that IT returns were not filed and let them impose tax What is your opinion? Kindly guide me